"It's pretty shocking, really, that we've lost that much biodiversity in such a short time," said one of the study authors.
A monarch butterfly perched on wildflower blossoms.
(Photo: Susan Gary Photography/Getty).
Eloise Goldsmith
Mar 06, 2025
COMMON DREAMS
A landmark study released Thursday in the journal Science found that the number of butterflies in the United States declined dramatically between 2000 and 2020.
"The prevalence of declines throughout all regions in the United States highlights an urgent need to protect butterflies from further losses," according to the abstract of the study, which was authored by over 30 researchers from around the country.
Between 2000 and 2020, total butterfly abundance in the contiguous United States fell by 22% across 554 recorded species. The study also reported widespread species-level decline, in addition to overall abundance decline. According to researchers, 13 times as many butterfly species are declining as they are increasing.
"It's pretty shocking, really, that we've lost that much biodiversity in such a short time," said Eliza Grames, a conservation biologist at Binghamton University in New York and one of the study authors, who spoke with WBUR about the findings.
The survey used data from multiple sources, including North American Butterfly Association, which is the "longest-running volunteer-based systematic count of butterflies in the world," as well as data from Massachusetts Butterfly Club, which "carries out organized field trips and records individuals' reports across the state in which participants identify and record butterflies seen."
Scientists and dedicated amateur enthusiasts helped collect the data, according to The Washington Post, which spoke with some of the researchers.
"Scientists could not get all the data we used," Nick Haddad, an ecologist and conservation biologist at Michigan State University who worked on the study, per the Post. "It took this incredible grassroots effort of people interested in nature."
The study identified pesticide use, climate change, and habitat loss as drivers of the decline.
The research echoes other scientific findings that have recorded widespread loss of insect abundance more generally, a phenomenon that's sometimes called the "insect apocalypse." Bugs do many important things, like pollinating crops and keeping soil healthy. "As insects become more scarce, our world will slowly grind to a halt, for it cannot function without them," wrote biologist Dave Goulson in 2021.
Entomologist David Wagner, who was not involved in the study, told the Post in an email that butterflies function as a "yardstick for measuring what is happening" among insects generally. He said the findings of the study were "catastrophic and saddening."
Study raises the possibility of a country without butterflies
Michigan State University
image:
A pair of dorcas copper butterflies, a North America native species, and one of the 324 species studied in this report.
view moreCredit: Photo by David Pavlik, Michigan State University
Butterflies are disappearing in the United States. All kinds of them. With a speed scientists call alarming, and they are sounding an alarm.
A sweeping new study published in Science for the first time tallies butterfly data from more than 76,000 surveys across the continental United States. The results: between 2000 and 2020, total butterfly abundance fell by 22% across the 554 species counted. That means that for every five individual butterflies within the contiguous U.S. in the year 2000, there were only four in 2020.
“Action must be taken,” said Elise Zipkin, a Red Cedar Distinguished Professor of quantitative ecology at Michigan State University and a co-author of the paper. “To lose 22 percent of butterflies across the continental U.S. in just two decades is distressing and shows a clear need for broad-scale conservation interventions.”
Zipkin and her MSU colleague and co-author Nick Haddad, professor of integrative biology, have been major figures in drilling down the state of U.S. butterflies. Zipkin has been a formidable numbers cruncher with successes gleaning hard facts from imperfect data sets to better understand the natural world.
Haddad is a terrestrial ecologist – a scientist on the ground specializing in the fates of the most fragile and rare butterfly populations. The widespread decline of butterflies found in this study have shaken Haddad, and reports that the mountain of data is on display in his Michigan neighborhood.
“My neighbors notice it,” Haddad said. “Unprompted, they’ll say, ‘I’m seeing fewer butterflies in my garden, is that real?’ My neighbors are right. And it’s so shocking.”
In this paper, Zipkin and Haddad were among a working group of scientists with the USGS Powell Center for Analysis and Synthesis that aggregated decades of butterfly data from 35 monitor programs that included records of over 12.6 million butterflies. Using data integration approaches, the team examined how butterfly abundances changed regionally and individually for the 342 species with enough data.
Abundance is a term that threatens to become ironic. Butterfly populations dropped an average of 1.3% annually across the country, except for the Pacific Northwest. But even that encouraging result came with a caveat. Further scrutiny of the apparent 10% increase in overall abundance in the Pacific Northwest over the 20-year study period was credited largely to the California tortoiseshell butterfly, which was enjoying a population boom not expected to be sustained.
Butterflies are the most surveyed insect groups, courtesy of extensive volunteer-based and expert science monitoring programs. Until now, studies have focused on individual species – most notably monarch butterflies – or limited to specific locations.
This new study uses all the available regional butterfly monitoring data within the continental United States and then develops a method of analysis that appropriately accounts for variations in collection protocols across programs and regions to produce comparable results for hundreds of species.
“This is the definitive study of butterflies in the U.S.,” said Collin Edwards, the study’s lead author. “For those who were not already aware of insect declines, this should be a wake-up call. We urgently need both local- and national-scale conservation efforts to support butterflies and other insects. We have never had as clear and compelling a picture of butterfly declines as we do now.”
Edwards had been a postdoctoral research associate at Washington State University, Vancouver, and now works at the Washington Department of Fish and Wildlife.
The results reveal that 13 times as many species declined as increased – with 107 species losing more than half their populations.
Zipkin and Haddad say butterflies are more than fluttering symbols of freedom and beauty. They play important roles in cycling nutrients and are a significant food source for other organisms such as birds. Over the last 50 years, North America has lost nearly 3 billion birds, a decline at almost identical rates of the butterflies.
Butterflies are important and forgotten pollinators. People often think of bees first, but butterflies (and flies) are responsible for $120 million of cotton production in Texas, for example.
Zipkin said she sees this paper as an important heads up to the country’s policymakers. “People depend on plants, microbes, and animals for the air we breathe, the water we drink, and the food we eat. Yet, we are losing species at rates that rival the major mass extinction events on our planet,” Zipkin said. “The U.S. plays an important role in setting policies and creating laws that conserve and protect biodiversity from local to global scales. Our leaders and the federal government, in particular, are responsible for making sure future generations have the necessary resources to thrive.”
In 2024, Haddad was part of a study published by the journal PLOS ONE that pinpointed the danger of insecticides, that rose above other threats such as habitat loss and climate change in reducing butterfly abundance and diversity. He points out that saving butterflies isn’t a hopeless problem, just one that requires will.
A lot of insecticide use, he said, lacks strategy and results in overuse. Some 20 percent of cropland suffers from poor yields. Creating policies that return under-producing land to nature could help the butterflies to rally.
“Prophylactic and near-universal application of insecticides harms butterflies and other beneficial insects, with no proven benefit to crop yield,” Haddad said. “What is applied as ‘insurance’ is extracting a great debt to agroecosystems. The good news is that the widespread application of insecticides can be reversed, and butterflies and other pollinators will recover.”
In addition to Zipkin, Haddad, and Edwards, “Rapid butterfly declines across the United States during the 21st century” was written by Erica Henry, Matthew Forister, Kevin Burls, Steven Campbell, Elizabeth Crone, Jay Diffendorfer, Margaret Douglas, Ryan Drum, Candace Fallon, Jeffrey Glassberg, Eliza Grames, Rich Hatfield, Shiran Hershcovich, Scott Hoffman-Black, Elise Larsen, Wendy Leuenberger, Mary Linders, Travis Longcore, Daniel Marschalek, James Michielini, Naresh Neupane, Leslie Ries, Arthur Shapiro, Ann Swenger, Scott Swengel, Douglas Taron, Braeden Van Deynze, Jerome Wiedmann, Wayne Thogmartin, and Cheryl Schultz.
Zipkin and Haddad are members of MSU’s Ecology, Evolution, and Behavior Program, of which Zipkin is director.
A zebra longwing butterfly is native to North America, and one of the 324 species studied to understand population decline.
Credit
Photo by Finn Gomez, Michigan State University College of Natural Science
Journal
Science
Article Title
Rapid butterfly declines across the United States during the 21st century
Article Publication Date
6-Mar-2025
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